This invention relates to an improved self-aligning bearing.
Self-aligning bearings for rotary shafts are known which have a convex spherical inner member or "ball" disposed within a matching concave outer member or "ball socket". The ball typically has a central cylindrical bore which provides a bearing surface for the rotary shaft. Such bearings typically have a solid ball with a continuous outer surface. The ball in such applications is typically die cast, sintered or machined. If a higher quality material such as a self-lubricating material is desired, then a sleeve of such material is inserted into the solid ball. This results in a multi-part bearing which is expensive to manufacture and expensive to buy.
Self-aligning bearings allow for less expensive brackets or other supporting structure to be used for the support of rotating motor shafts. Parts made to less demanding tolerances are cheaper to make and can be assembled with somewhat less care and precision with satisfactory results. For most motor shafts, it is absolutely imperative that the internal diameter of the bearing line up with its mate or there will be a bind on the rotating shaft resulting in poor performance.
Prior designs have not been able to accomplish this with a bearing that can be produced in a die that has only two parts or which does not cause an irregular surface on the bore of the bearing called "sink marks".
These sink marks are the result of intersecting mold walls. Thus, for example, bearings have been molded with radial fins but the internal diameter is marred by these sink marks, thus destroying the smoothness of the internal diameter or bearing surface. There is thus a need for an inexpensive, self-aligning bearing which has a uniform, self-lubricating inner bearing surface.
Accordingly, it is among the several objects of the present invention to provide a low cost bearing which can be accurately and rapidly molded in a relatively inexpensive, single action, two-piece mold.
It is also an object of the present invention to design a bearing which is self-aligning and yet can be produced in a two-part mold with no side cores, no abnormally thick sections, and no internal diameter irregularities such as sink marks or the like.
It is a further object of the invention to provide a relatively long-lasting bearing.
These needs are satisfied by the present invention which provides an inexpensive one-piece plastic self-aligning bearing which includes a cylindrical bearing sleeve of uniform thickness having an outwardly convex hemispherical flange projecting from a first end of the sleeve and arching longitudinally toward an opposite second end of the sleeve, the flange being of uniform wall thickness.
The bearing sleeve preferably has an outwardly concave hemispherical flange at each end to produce a hollow spherical outer wall with two hemispherical portions, a center of one portion being attached to a first end of the inner wall and a center of the other portion being attached to the opposite end of the inner wall. The outer rim of each hemispherical flange is preferably connected to the outer rim of the other hemispherical flange to provide increased strength and rigidity to the outer wall portion. The hemispherical portions preferably have a plurality of axially tapered segments separated by axially tapered spaces of equal size to facilitate one-piece injection molding of the entire bearing. The wall portions are preferably of uniform thickness.
Other objects will be in part apparent and in part pointed out hereinbelow.